British light-heavyweight Joshua Buatsi made a winning yet disappointing start to life under new promoters with a decision win over Parker in Manchester.
The Olympic bronze medallist's punch output seemingly secured him a judges' verdict in a close ten-round fight at the Manchester venue.
But Parker found success, landing some telling single shots in a contest where the approaches failed to mesh, with constant grabbing disrupting the action.
Two judges judged it 96-94 for to Buatsi, with the final judge a 95-95 draw.
"It wasn't my best performance but what do champions do? They succeed," the victor stated in the ringside as he was met by negative reactions from the spectators.
The Londoner got back to winning after his maiden career setback - an epic battle with his previous opponent in February - to earn a 20th pro success.
Some ringside observers felt Parker, 31, should have been awarded the decision but the Derbyshire fighter experienced the second setback of his 28-match career.
The Champion Secures Triumph in Slow Affair
The fighter's advancement has plateaued in the past few years through management issues and considerable time of inactivity.
Once tipped as the next star of UK boxing, he now finds himself trying to fulfil that early promise - perhaps in what appears to be a ultimate opportunity - under recent support.
He opened tentatively, with the two boxers willing to be aggressive in a cagey opening few rounds.
The challenger, whose sole prior loss came at super middleweight against John Ryder in two years ago after damaging his hand in the contest, was participating in his second fight at the higher weight class.
By the middle rounds, Parker had stayed in contention, creating difficulties for the favorite, who worked behind a solid defense to edge the more effective rounds.
The spectators' acceptance diminished because of frequent holding, with Parker slipping to the canvas various instances during close exchanges.
Parker closed well, but many rounds were challenging to assess. However, previous titleholder Carl Frampton - working with the broadcast network - had it significantly in favor for the challenger, scoring for Buatsi just only one stanza.
The victor progresses, but with the likes of power puncher Benavidez, and Russian champion Dmitry Bivol ruling the division, the path to championship success - on this evidence - still looks steep.
Ricky Hatton Memorial Motivates Manchester Derby Fight
In the co-main event, Arthur beat Bradley Rea by close verdict in a terrific local rivalry contest to capture the European light-heavyweight belt.
The arena grew hushed for a profoundly moving memorial before the fight as a bell ceremony tolled in remembrance of the city's native Hatton, who died 46 years old in recently.
It was the first major televised fight night in the urban center since the passing of Hatton. As the last bell disappeared, the silence transitioned to a roar of "there's just one Ricky Hatton".
The action inside the ropes reflected the feeling. The eventual winner was knocked down by a powerful punch directly to the jaw in the early round, rising shakily to his position on the eight count.
But the red-colored shorts of Arthur soon advanced again. From the other corner, Rea - in rival City blue - was damaged quickly, heavy swelling developing under his eye as the duo traded powerful shots.
The challenger, twenty-seven, connected with strong blows but Arthur, thirty-four, matched the intensity with effective uppercuts as the action hardly diminished over twelve rounds.
The victor edged the decision with judges scorecards of even score, narrow lead and 115-112, but the two athletes were determined and full of heart, exactly what their idol Hatton embodied.
